Reduced Delayed Neutron Group Representations

Abstract

It has been shown (1) that a two-delayed neutron group model will accurately represent the asymptotic behavior of the reactor transfer function. Correspondingly, the requirement that this asymptotic behavior be accurately represented is sufficient to specify completely the two-delayed neutron group constants. Further, a three-delayed neutron group model has been evolved which is designed to represent both the asymptotic behavior of the transfer function and shutdown behavior. The inhour equation, transfer function, and transient behavior for step inputs of reactivity with and without reactivity feedback loops for the two- and three-delayed neutron group representations are compared with those given by the standard one group and many delayed neutron group treatments. Important consequences of such reduced group representations are savings in machine time in making kinetic studies and increased tractability of the reactor kinetic equations.